The term flue-gas pipe is used hereinafter to refer to exhaust gas pipes to carry off gas by overpressure as well as gas pipes to carry off hot and, under certain circumstances, acid exhaust gases through thermal suction. The latter gas pipes are typically found as chimney arrangements, and since the introduction of modern low temperature, cyrogenic and/or condensing value boilers, also as flue-gas pipes, known as diminished cross-section, subsequently installed in existing chimney arrangements.
Exhaust gas pipes and diminished cross-sections for chimneys, known as chimney pipe systems, are produced from pipes sealed together. Ceramic materials, dead-burned fireclay, and glass, but also metal materials, preferably stainless steel, are used as materials for these pipes.
Although identical tubes are used for both types of pipe, exhaust gas pipes and chimney pipes, there is thus far no uniform piping and sealing system for exhaust gas pipes and chimney pipes, in particular diminished cross-sections. This is due to the fact that different demands are made on the sealing of these pipes.
Sealing for exhaust gas pipes must guarantee that the exhaust gas released with overpressure cannot escape at the pipe joints and that any condensing humidity cannot escape. Sealing for chimney arrangements, on the other hand, are subjected to stress high exhaust gas temperatures and highly acid condensates.
In the case of exhaust gas pipes, for example, stainless steel pipe sections are connected together by silicon-rubber seals. These silicon-rubber seals may well provide adequate tightness for changing pressure conditions, but they have only a limited chemical and temperature resistance. Stainless steel pipe sections used in chimney arrangements, on the other hand, are mounted by simple plug-in connections.
Ceramic pipes, and pipes made of dead-burned fireclay, are also sealed with silicon seals, in this case as silicon sleeves, for gas pipes. Glazed ceramics are usually used in exhaust gas pipes. Due to the inadequate acid and heat resistance of silicon sleeves, the same pipe sections are designed, when used in chimney arrangements, as pipes with groove and tongue that are connected with acid-resistant putty. However, this type of connection by groove, tongue and putty is not tight enough to guarantee that in the case of changing pressure conditions in exhaust gas pipes, for example, that the exhaust gas will not squeeze out at the pipe joints.
Pipes of glass, when used for exhaust gas pipes, are also joined together with silicon-rubber seals. Chimney arrangements are, however, sealed more expensively, for example according to the process described in German Patent 38 21 019: A mineral spacer ring is used between the glass pipes at the pipe joint, the pipe joint is wound on the outside with a mineral fiber strip fixed with anorganic adhesive, and the closing connection of the two pipes is made by a stainless-steel clamp fitting. This connection is also not sufficiently gas-tight for exhaust gas pipe use.
The different demands on sealing systems for use in exhaust gas or chimney arrangements are clearly shown in the requirements compiled by the Institute for Bautechnik (IfBt) in Berlin. Sealing systems for exhaust gas pipes must be able to withstand a pressure change from -1,000 mm WS to +40 mm WS. Chimney arrangements, on the other hand, must be able to withstand flue-gas temperatures of 40.degree.-500.degree. C.
In addition, seals for chimney arrangements, as explained above, must be sufficiently acid-resistant not to be decomposed by highly acid condensates that, among others, are given off by modern home heating systems such as low temperature, cyrogenic and/or condensing value boilers.
As is shown by the preceding description, a specific seal is required depending on the use of the pipes. This multiplicity requires not only great production, distribution and storage expense, but installation errors and thereby dangerous malfunctions of the pipe system can also occur under certain circumstances.
Numerous pipe connections to connect and seal two pipes are known from the state of the art; for example, from U.S. Pat. No. 2,302,244. Other papers describe the centering of two overlapping pipe ends, thus providing a uniform, annular gap to insert the sealing mass. Such centering arrangements are, for example, the subject of U.S. Pat. No. 2,310,122, German DE-GM 19 76 874 and German DE-AS 26 00 621. A disadvantage of these arrangements is the fact that the pipe ends to be connected cannot be moved until the sealing mass has completely hardened, if tightness or resistance of the connection is to be guaranteed.